Tutorial: How to overclock your RAM

How to overlock your RAM

Overclocking memory isn't quite the ticker-tape parade of increased performance found when boosting your GPU or CPU, but that doesn't mean it shouldn't be considered. A lot of memory comes boasting great overclockability (of course it's a word) but many builders are so keen on tweaking other components, they plum forget all about it.

Whilst tweaking your RAM is unlikely to yield noticeably higher frame rates in your favourite games, it can make a big difference to desktop use and file operations - and that alone makes it worth it. Plus, overclocking is one of the many things that make being a PC owner so great. We'd overclock our keyboards if we could.

But how does one get the most out of those innocuous sticks of RAM? There are a number of approaches, and like CPU overclocking your best bet is to head into the BIOS. Since we mentioned CPUs, if you're already running your CPU overclocked that will affect your RAM; particularly if you've increased the BLCK setting.

Likewise, upgrading your rig with high performance, high-headroom RAM can open up further possibilities for boosting your CPU. Intel 6 series chipsets (H61, H67, P67 and Z68) are highly integrated fellas.

The reason you can't get far by boosting the BLCK anymore is because you're overclocking the whole Northbridge, which controls both the PCI-e and RAM clock settings too, and it's a big ask to demand all your other components overclock as well as your CPU and its huge cooler.

Hertz me so

Thus, increasing BLCK is best used as a final measure to squeeze a few final Hertz from your CPU. If you've got RAM that can withstand timings as high as 2,133MHz though, you can squeeze a few Hertz more still, but it's memory frequency and latency that will give you the big RAM overclocks.

When you've raised all these elements to their limits, there's still voltage increase to consider. Increasing voltage is like getting an overdraft - it buys you more room for manoeuvre, but increasing it by too much can be dangerous. We'd advise 1.7V is as high as you'd need to go; you could probably go higher without causing permanent damage, but it probably wouldn't allow you that much more performance.

Project goal: Hit the rated speeds

A lot of RAM is sold as overclocking-grade these days, but to squeeze the rated speeds out of your particular sticks will require a little overclocking nouse.

Wringing out the RAM

But we ought to be wringing every last drop of performance from our memory. By the end of this tutorial you'll be lowering the latency of your RAM like my tenuous metaphors lower the bar for humour in this mag.

What's needed:

A decent set of DDR3 RAM If you've got G.Skill's monstrous RipJawsX from the gaming rig in our system building feature then happy days. Those blue sticks overclock incredibly well. Otherwise pick a kit with high rated frequencies and that's got low-latency and/or low voltages.

Jargon explained

CAS Latency: Time between the CPU asking for data and RAM releasing it.

RAS to CAS delay: Time to organise a Row Access Strobe line and Column Access Strobe in memory.

RAS Pre-charge: Or rTP, the time taken to disable one RAS line and active the next.

Active to pre-charge delay: Or tRAS, the time taken between memory access.

Memory tweaking tips

Six different ways to make the most of your memory

01. Enter the BIOS

The BIOS: Incomprehensible to some, but to the overclocker it's home. Here you'll find DRAM frequency, usually located in modern EFI BIOS' overclocking/volting options screen.

Most DDR3 RAM runs at 1,333MHz, but overclocking RAM such as G.Skill's RipJawsX will happily run at 2,133MHz. Ramp it up incrementally, though. If your PC boots, restart it and increase the frequency some more.

02. Test your settings

Run the memory bandwidth test in SiSoft's Sandra. This will also give you an idea of just how much you've increased your memory throughput with the boosted RAM.

Running a game won't give you much feedback; it's desktop responsiveness and speedy file operations you're after, so if your system remains stable while kicking about with Sandra, it's time to push it further.

03. BCLK tweaking

You probably won't get past 2,133 MHz in the DRAM frequency menu because the options go up in such large chunks, but that's not the end of the road for frequency boosting.

You can use the BCLK (usually in the same BIOS menu) to raise CPU and RAM frequency together, and in much smaller increments - by 0.5 if need be. Remember though, you are overclocking the CPU as well…

04. Knowing me, knowing CPU

…which makes it harder to pinpoint exactly how much extra performance is coming from memory. Again, SiSoft's Sandra will give you accurate readouts by stressing memory only.

If you've already overclocked your CPU within an inch of its life, including the base clock, obviously there's no further boost you can give to memory frequency here.

05. Know your SPD

The other pot o' performance gold is latency. To start tweaking this you'll need to know your RAM's stock SPD settings. CPU-Z will put you in the know with its SPD tab.

They should read something like 7-8-7-24. Each number relates to the time it takes to perform specific functions - CAS latency, RAS to CAS delay, RAS precharge, and active to precharge delay.

06. Reduce latency

For overclocking, you'll want to focus your attention on CAS latency, which is the time it takes between the CPU to ask for data and memory to provide it. A lower response time is obviously better, so find CAS latency in your BIOS' DRAM timings screen, and lower it by as little as possible.

If you ramped up frequency first, you'll likely be working back towards the stock timing.

Benchmarks

Our unflappable G.Skill RipJawsX 4 GB kit got put through its paces on an Asus P8Z68 V Pro board with a Core i5 2500K. We found the best performance increase in both synthetic and real-world tests came from increasing memory frequency.

Lowering CAS latency reaped its own benefits, but we found the balance between the two should favour increased frequency.

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Tutorial: How to overclock the Intel Z68

How to overclock the Intel Z68

There's a lot to smile about when it comes to Intel's latest chipset; Z68 puts right the silly mistakes and arbitrary differences between P67 and H67 platforms, and one of the biggest improvements is overclocking.

If you've got a Z68 motherboard, you can increase your core multiplier, DDR3 memory ratios, boost your power and current limits - as you can on the P67 platform.

Where the Z68 differs from the P67 chipset, though, is in the processor graphics core of the Sandy Bridge chips. You can overclock that too, at the same time as CPU core multipliers. That means you can get faster frame rates if you're playing games with on-die graphics, and reap the general benefits of a quicker CPU, all at once.

So why should you overclock your system if you have a Z68 motherboard? Well, simply because you can. Because previous Sandy Bridge chipsets didn't allow this freedom, and because Sandy Bridge CPUs themselves have tons of overclocking potential. But first…

A word of warning though. Tweaking your CPU and graphics at the same time is nothing new, but when a discrete card's providing the grunt, power and current are increased over separate areas of your computer, and the same goes for temperature. When the graphics are on die though, all the extra performance you dial in comes from one rather delicate two centimetre slice of silicon. As a result, it's harder to keep temperatures in the safe zone.

Moreover, the benefits of tweaking the iGPU and CPU at the same time are dubious. We noticed that at times performances actually dropped when we boosted them both, likely due to all that heat and throttling. It's a balancing act boosting them to the right amount. Get it right though and you can boost the iGPU to produce frame rates that really make the difference between unplayable, playable, and infuriating.

Our test rig for this project is an Intel Core i7 2600K in an Asus P8Z68 V Pro, cooled by CoolIt's ECO ALC water cooler. We've seen very impressive numbers posted by that CPU, as high as 5.2 GHz on enthusiast mobos like the MSI Big Bang Marshal. With some diligent tweaking we squeezed a very stable 5.0 GHz out of it. Bearing in mind we used a relatively cheap cooler and motherboard, that ain't half bad.

Every CPU and motherboard has its own overclocking threshold though, and results can vary significantly between seemingly identical chips, particularly the amount of voltage they can hack. So this guide isn't about achieving a certain GHz, it's about getting the most from your particular system.

Right, now lets get elbow-deep into all the funky BIOS options your Z68 motherboard has to offer and see what we can get out of this chip.

1. Let The BIOS do the work

The simplest overclocking method is to run an auto-overclock procedure like Asus' OC tuner. With one click you'll get a useful slice of extra performance auto adjusting CPU ratio, voltage and BCLK frequency. Your rig might restart a few times before it finds the best settings. The downside to this technique is that it doesn't absolutely push the boundaries the way you could by tweaking manually…

2. Know your settings

…and if you're going to get your hands dirty, the key settings to examine are CPU ratio and CPU Vcore. Ratio's going to ramp up your core clock frequencies and Vcore is the main source of power for your CPU. Most of your time is going to be spent tweaking these two settings. It's useful at this point to turn off SpeedStep and set Load Line Calibration to auto. This will avoid throttling at higher temps.

3. Learn your multiplication tables

CPU ratio (aka multiplier) will accept any number between 34 and 56, which would hypothetically give a stonking 5.6GHz. Tiny increments are the key: ramp up the multiplier in twos. If your system boots, load up a CPU-heavy benchmark like Cinebench 11.5 and run it a few times. If it passes the stress test, head back to the BIOS and increase the ratio by another 1 to 2.

4. Trial and error

Eventually you'll hit a wall and crash. Here's where Vcore comes in. You want to run with as little voltage as possible, so when you've maxed the ratio, increase the Vcore a little to give your CPU more juice. The sweet spot is around 1.44V to 1.55V, but again, increase slowly and stress test if it boots. Ignore CPU PLL and PCH-increasing these voltages won't give you any more overclocking room.

5. Push the limits

If you over-volt, you'll get a POST screen error message. Go back to your last good setting, then try increasing the ratio some more. When you max both ratio and Vcore, you can still squeeze a drop more from BCLK/PCI-e, so try adding 1 to the current value. Depending on your RAM speeds, you may need to actually clock it down to find an appropriate speed for your memory.

6. One-stop graphics boost

To boost processor graphics performance, iGPU max frequency is your man. As mentioned the benefits of clocking CPU and iGPU at the same time are questionable, but increasing the iGPU frequency by just 100MHz will give you higher frame rates. Stress test with a gaming benchmark then reboot and increase by another 50MHz or so. Voila. You've made full use of the overclocking features of Z68 gratis.